Slack, Teams, and Discord are proof that there are serious demands to have a chat system. It's just IRC as it is, is clearly outdated for the current market.

It's niche is as simple as it was way back when, you can create your own chat server for your community. Instead of having to use Discord, Slack, etc you can create your own and control it fully. While it's possible to do that to this day it's not to the same level it was back in the late 90s for example.